Diametrically opposite to tokens beyond 200K being literally free? As in, you only pay for the first 200K tokens and the remaining 800K cost $0.00?

I don't think that's a fair reading of the original post at all, obviously what they meant by "no cost" was "no increase in the cost".

I can see that's what they mean now that I've read the replies, but when I first read that top comment I too parsed it as meaning 201k would cost the same as 999k (which admittedly did seem strange, hence I read the replies to confirm and sure enough that's not actually the case!)